Haüyne

What is haüyne? The IMA row and the sheet

Haüyne is a cubic sodium calcium aluminosilicate with sulphate in its cages, Na3Ca(Si3Al3)O12(SO4) on the September 2026 IMA list. The list gives status G (grandfathered), 1807, Italy, with a first reference in the Journal des Mines 21 (1807), 365. The Handbook of Mineralogy haüyne sheet writes a general formula instead, (Na,Ca)4–8Al6Si6(O,S)24(SO4,Cl)1–2, which spans the analyses it prints; doubled, the IMA formula is Na6Ca2(Si6Al6)O24(SO4)2, inside that range. Both spell the name Haüyne; hauyne, without the diaeresis, is the same name unaccented.

On the sheet. Cubic, point group −43m (read from the rendered sheet), as dodecahedra or pseudo-octahedra to 3 cm and in rounded grains, with twinning on {111} common, rarely as penetration twins, also polysynthetic or contact twins. Cleavage {110} distinct, fracture uneven to conchoidal, brittle, hardness 5.5 to 6, measured density 2.44 to 2.50. Transparent to translucent, bright blue to greenish blue, also white or shades of black, gray, brown, green, yellow or red, and may be patchy; streak slightly bluish to colourless; lustre vitreous to greasy. Isotropic, weakly birefringent when included, n = 1.494 to 1.509.

Group and name. The sheet prints Mineral Group: Sodalite group. The name honours Abbé René Just Haüy (1743–1822), French crystallographer and mineralogist. How the group is counted from the sheets is on sodalite and is not repeated here.

How is haüyne different from sodalite, nosean and lazurite? The Ca–SO4 key

Calcium separates haüyne from sodalite and nosean, and the amount of it, with the absence of an S3 group, separates it from lazurite. Written per Al6Si6O24 framework, the IMA formulas give: haüyne 2 Ca and 2 SO4; lazurite 1 Ca, 1 SO4 and one S3 group; nosean no Ca and 1 SO4, with water; sodalite no Ca and no sulphate, with 2 Cl. The IMA list has no group column; the four are linked here because each Handbook sheet prints Sodalite group.

Worked as an analysis would read. On standard atomic weights the ideal haüyne formula is Na2O 16.53, CaO 9.97, Al2O3 27.20, SiO2 32.06 and SO3 14.24 wt%. Nosean’s ideal is CaO 0 and SO3 7.91, with H2O 1.78, the same figures its sheet prints for the ideal. Lazurite’s IMA formula gives CaO 4.98 and, counting its SO4 alone, SO3 7.11, with 11.39% sulphur in all. Sodalite’s is CaO 0, SO3 0 and Cl 7.32, the figure on sodalite.

The key against real analyses, and where it blurs. The haüyne sheet’s Monte Vulture analysis recalculates to 1.80 Ca and 1.33 SO4 with 0.22 Cl and 1.22 K; Anguillara to 2.26 Ca and 1.86 SO4. Both sit near 2 Ca. But the nosean sheet’s analysis from Covao, Cape Verde Islands, has CaO 4.40, about 0.8 calcium for every six silicon worked from its oxides, close to lazurite’s 1. Natural material runs between the ideal formulas, so the key names the end-members; a borderline grain needs an analysis, not a balance.

How do you tell haüyne from lazurite? Weight fails, streak works

A balance cannot separate haüyne from lazurite: a 20.00 g piece reads 11.80 to 12.00 g in water as haüyne and 11.60 to 11.84 g as lazurite, an overlap of 0.04 g. Worked as 20 − 20/D on the sheets’ measured densities, 2.44 to 2.50 and 2.38 to 2.45. Nosean reads 11.30 to 11.67 g and sodalite 11.19 to 11.42 g, so a reading of 11.80 g or more rules out those two on their sheets. The method is on how to measure specific gravity at home.

The streak does what the balance cannot. The haüyne sheet gives slightly bluish to colourless; the lazurite sheet bright blue; sodalite’s white. A strongly blue streak points at lazurite, a nearly colourless one at haüyne or sodalite. Streak technique is on how to use a streak plate.

Rock against mineral. Lazurite is the blue mineral of lapis lazuli, and the sheet’s association line for lazurite includes haüyne. Whether a blue stone is the rock or one mineral is on is lapis lazuli a mineral or a rock; the separation of sodalite from lapis, with its own weight line, is on is sodalite the same as lapis lazuli.

Is haüyne fluorescent?

The haüyne sheet says it may show reddish orange to purplish pink fluorescence under LW UV, and names no shortwave response. The line was read on the rendered sheet as well as the text layer, because pdftotext writes the fl ligature in fluorescence as a stray glyph. Sodalite’s sheet, by contrast, prints bright red-orange under both LW and SW with a yellowish phosphorescence; the comparison of all four sodalite-group sheets is on is sodalite UV reactive.

What this page does not add. The sheet gives no cause for the glow, and this page gives none. Lamps, wavelengths and the general picture are on fluorescent minerals explained and best UV lamp for mineral collecting.

Where haüyne is found

The Distribution field names, in Italy, many localities in the Alban Hills, Lazio, as at Ariccia, Marino, Sacrofano and Campagnaro; Monte Somma and Monte Vulture, Campania; and the Pitigliano quarry near Grosseto, Tuscany. In Germany, Mendig, Mayen and elsewhere in the Eifel district. In the USA, Winnett, Petroleum Co., Montana, and the Edwards mine, St. Lawrence Co., New York. Also the Niangniang Shan complex, Nanjing, Jiangsu, China, and the smaller island of Taiarupu, Tahiti; a few other localities are known.

How and with what. The occurrence field reads in phonolites and related leucite- or nepheline-rich igneous rocks, less commonly in nepheline-free extrusives. The association line is nepheline, leucite, titanian andradite, melilite, augite, sanidine, biotite, phlogopite and apatite.

Weighing it. A 20.00 g piece of haüyne reads 11.80 to 12.00 g in water; volcanic matrix changes the reading. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.

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